SAS/LAB software uses two-level names to refer to SAS data sets. The first level is a libref (a temporary name associated with a SAS data library) and the second level is the actual name of a SAS data set within a SAS data library.
For example, if a data set is called MYLIB.STRENGTH, MYLIB is a libref that is temporarily pointing to a particular SAS data library, and STRENGTH is the name of a SAS data set within that SAS data library.